Monongahela (mō-nǒn′gȧ-hē′lȧ), a river, one of the sources of the Ohio, rises in West Virginia, flowing north into Pennsylvania where it unites with the Allegheny at Pittsburg and forms the Ohio. It is 250 miles long, and is navigable for about 80 miles for large boats. Cheat River and the Youghiogheny are its chief branches. Here, on the banks of the river, near Pittsburg, was fought, July 9, 1755, a battle between the French and the Indians and the British and colonial troops under Braddock. The latter were beaten.